Bactericidal thin sol-gel films on metallic implants -- an in-vitro study

Periprosthetic infections are a major complication of joint replacement and other orthopedic surgeries. The majority of these infections are caused by S. aureus which, when they grow on an implant, develop into a bacterial biofilm. The bacterial biofilms are very difficult to kill and have resistances up to one thousand fold more than their planktonic counterparts. Therefore, it is desirable to have a technology which can prevent biofilm growth on implants. Herein we demonstrate that the room temperature silica sol-gel process can be used to form thin films incorporating vancomycin and farnesol on metallic implants. We evaluate the characteristics of these thin films and evaluate their bactericidal effects against methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). We determined that thin sol-gel films release drugs through degradation which is both time-dependent and drug-load-dependent. In addition, it is found that farnesol is useful for decreasing the "burst" release of vancomycin resulting in more controlled drug delivery. It was determined that farnesol has bactericidal effects against MSSA, but not against MRSA; however, farnesol worked well as an adjuvant to vancomycin. When farnesol was used as an adjuvant in combination with vancomycin, a 10 to 1000 fold decrease in bacterial film growth was seen on the implant. These results clearly demonstrated that the novel thin sol-gels films with vancomycin and farnesol can be used for targeted drug delivery on implants to substantially prevent bacterial biofilm growth.